The orthorhombic modification of CaPbO3 was synthesized from a mixture of Ca2PbO4 and PbO2 at high temperature and high pressure. Its structure was analyzed by Rietveld analysis of neutron diffraction data on the basis of space group Pbnm. It has a distorted perovskite structure of the GdFeO3 type and a unit cell with dimensions of a = 5.6710 A, b = 5.8875 A, and c = 8.1495 A. The Pb−O bond lengths in each PbO6 octahedron are comparable to each other, whereas the PbO6 octahedron tilts around [110]p and [001]p axes (p: perovskite subcell) by 18.50° and 20.28°, respectively. These tilt angles, which show great structural distortion in CaPbO3 containing the smaller Ca2+ ion, are much larger than corresponding ones in crystal chemically isotypic SrPbO3. The electric resistivity of CaPbO3 at room temperature was as high as 3 × 103 Ω•cm, which is in sharp contrast to low resistivities observed in other perovskite-type oxides BaPbO3 and SrPbO3. The high resistivity of CaPbO3 is explained as gap formation betwee...